Impact-opening electrical switch with breakable frangible element

ABSTRACT

Primarily for automotive use between the battery and the electrical system, the switch includes two stationary contacts normally bridged by a movable contact. The movable contact is biased by resilient means toward an open condition, but is normally held closed by a frangible element designed to be broken by a breaker element upon a change in momentum equal to a preselected threshold level of e.g. 10 miles per hour. The switch is preferably interposed in the battery cable on the &#39;&#39;&#39;&#39;hot&#39;&#39;&#39;&#39; side and mounted on the vehicle near the battery, e.g. on an engine compartment wall.

United States Patent 1 1 Six, Jr. May 22, 1973 [54] IMPACT-OPENING ELECTRICAL 2,806,915 9/1957 Fowler ..200/61.45 R SWITCH WITH BREAKABLE 2,538,581 1/1951 Minch et a1 ..200/16 A X FRANGIBLE ELEMENT FOREIGN PATENTS 0R APPLICATIONS [76] Invent Rute Emsmn 779,272 7/1957 Great Britain ..200/61,45 R

[22] Filed: Aug. 19, 1971 Primary Examiner-J. R. Scott A t C b C PP 173,222 torney ushman Dar y& ushman V [57] ABSTRACT [52] 11.8. CI. ..200/6l.45 R Primarily for automotive use betwew the battery and [51 Int. Cl- ..H01h 35/02 the electrical System the Switch includes two stationa [58] Field of Search ..200/61.43 R, 61.53, W contacts normally bridged by a movable Contact 200/168 F The movable contact is biased by resilient means toward an open condition, but is normally held closed Referencfi cued by a frangible element designed to be broken by a breaker element upon a change in momentum equal UNITED STATES PATENTS to a preselected threshold level of e.g. 10 miles per 2,223,097 11/1940 Ehret ..200/6L45 RUX hour. The switch is preferably interposed in the bat- 3,286,055 11/1966 Jewell ..200/61.45 R tery cable on the hot side and mounted on the vehi- 2,056,494 10/1936 Tucker, Jr. etal ..200/61.45 R cle near the battery, e.g. on an engine compartment 2,145,543 l/1939 Gross ..200/168 F wall 2,254,294 9/1941 Kimmell ..200/6l.45 R 2,778,896 1/1957 Tollefsen ..200/61.45 R 7 Claims, 2 Drawing Figures PATENTEnmYzems m T m V m FIG. 2.

q ATTORNEYS IMPACT-OPENING ELECTRICAL SWITCH WITH BREAKABLE FRANGIBLE ELEMENT BACKGROUND OF THE INVENTION When a motor vehicle has been involved in an accident, often the vehicle occupants are injured or shocked, or have been thrown from the vehicle, and do not, or cannot, turn off the ignition or disconnect the battery from the electrical system to prevent or reduce the hazard of an electric spark-ignited fire.

Others have designed switches to open or close upon impact. The present invention relates to a particularly useful design of such a switch. It is designed to be actu-. ated by momentum change in any generally horizontal direction.

In the prior art and known to the present inventor are the following:

The patent to Jewell U.S. Pat. No. 3,286,055 of Nov. 15, 1966, illustrates an impact switch which turns on a flashing warning light mounted on a vehicle. In this apparatus, a breakable rod is surrounded by a weight 25 which is designed to shift with impact. The breaking of the rod allows a switch to close.

The patent to Jennings U.S. Pat. No. 2,105,286 of Jan. 11, 1938, relates to a circuit breaker for vehicles which reacts to impact from a specific direction. A plunger, held in place by a shear pin, is used to break a fuse 9 to interrupt the flow of electricity.

The patent to Gross U.S. Pat. No. 2,154,543 of Jan. 31, 1939, relates to a safety device for motor vehicles in which mercury closes the contact between terminals 26 and 28 in a glass sphere 10. If the vehicle turns over, the mercury runs out of the sphere, breaking the contact. In addition, there is a rod 36 attached to the engine and placed in close proximity to the member 10. If the engine is displaced due to impact, this rod breaks the sphere, allowing the mercury to run out and break the circuit. I

The patents to Smith U.S. Pat. No. 2,475,728 of July 12, 1949, and Fowler U.S. Pat. No. 2,806,915 of Sept. 17, 1957, are of general interest as they also illustrate collision activated switches.

SUMMARY OF THE INVENTION Primarily for automotive use between the battery and the electrical system, the switch includes two stationary contacts normally bridged by a movable contact. The movable contact is biased by resilient means toward an open condition, but is normally held closed by a frangible element designed to be broken by a breaker element upon a change in momentum equal to a preselected threshold level of e.g., 10 miles per hour. The switch is preferably interposed in the battery cable on the hot side and mounted on the vehicle near the battery, e.g., on an engine compartment wall.

The principles of the invention will be further hereinafter discussed with reference to the drawing wherein a preferred embodiment is shown. The specifics illustrated in the drawing are intended to exemplify, rather than limit, aspects of the invention as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWING In the drawing: FIG. 1 is a vertical longitudinal sectional view of the presently preferred embodiment of the impact switch incorporated in the electrical system of an automobile adjacent the electric storage battery thereof.

FIG. 2 is a fragmentary sectional view comparable to the central portion of FIG. 1, following breakage of the frangible element.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT The switch 10 includes a housing 12, which, in the instance depicted, has a rectangular tubular sidewall 14 closed at each end by covers 16,18 which screw in place with peripherally located screws 20.

Two diametrically opposed openings 22 in the housing sidewall 14, respectively, receive two stationary contacts 24 which protrude toward one another within the housing and project exteriorly of the housing. Exteriorly of the housing, the contacts 24 are each provided with a socket 26 intercepted by an adjustable set screw 28. When the switch is in its preferred use, the battery cable 30 on the hot side of the battery is severed; its insulation is stripped back a short distance and the two bare ends 32 are jammed into the respective sockets 26 and secured in physical and electrical contact with the stationary contacts 26 by screwing in the set screws 28.

Within the housing, the inner ends 34 of the contacts 24 lie spaced from one another on a horizontal line proceeding diametrically of the housing. The inner ends 34 are preferably disposed at angles to one another and to the vertical, as shown.

The switch 10 further includes a movable contact 40, shown having a generally trapezoidal vertical crosssectional shape (larger base down), with its two opposite outer end surfaces 42 cut at angles complementing those of the stationary contact end surfaces 34. The size and spacing of the contacts is such that the movable contact 40 may be wedged between the inner ends of the two outer, stationary contacts 24, with the two respective sets of end surfaces 34,42 in engagement with one another so long as the switch is in a normal,

. closed condition.

The movable contact is shown mounted via a screw 44 onto the underside of a slide element 46 disposed for vertical sliding movement within the upper part of the housing. The periphery of the slide 46 matches the internal periphery of the housing in said upper part, but is slightly smaller so that the slide is guided by the internal peripheral surface 48 of the housing. I

An upwardly opening well 50 is formed in the upper end of the slide 46 coaxially with the screw 44 and the movable contact 40. A normally compressed coil spring 52 is received in the well 50 and projects upwardly therefrom into contact with the underside of the upper end cover 16 of the housing. The upper end of the spring surrounds a positioning boss 54 formed on the center of the underside of the upper end cover 16.

The underside of the movable contact 40 has a shallow recess 56 therein wherein the head 58 of the screw 44 is partially recessed. The recess 56 has a greater diameter than the screw head 58.

The lower end cover 18 also has a boss 60 formed centrally on the inner, upper surface thereof, a tube 62 of frangible material, e.g., glass is positioned between the upper surface 66 of the lower end cover 18, surrounding the boss 60, and the lower surface 68 of the movable contact, within the recess 56. The frangible tube 62 is sufficiently long that it forces the slide 46, screw 44, contact 40 (now designated the movable contact assembly 77) upwardly against the restoration force of the spring 52 and maintains the movable contact in physical and electrical contact with the stationary contacts, so long as the frangible tube 62 remains unbroken.

A secondary compression coil spring 70 may be provided within the tube 62 with its lower end in contact with the lower end cover 18 (e.g., upon the boss 60) and with its upper end in contact with the underside of the movable contact assembly 77. The spring 70 takes some longitudinal compressive stress off the frangible tube 62 and assists in maintaining the switch in a normally closed condition so long as the frangible tube shall remain unbroken. (The upper spring 52 is stiffer than the lower spring 70 so the former will overcome the latter when the frangible tube is broken.)

The device further includes a breaker for the frangible tube. The breaker 80 is shown having the form of an annulus of relatively heavy material, axially shorter than the distance between the movable contact and the lower end cover of the housing. The breaker 80 loosely surrounds the frangible tube and preferably includes in its bore 82 one or more circumferential ridges 84 which bear against the frangible tube intermediate the ends of the frangible tube, or are spaced a short distance radially thereof.

When the device is in use, an impact on the vehicle in any horizontal direction including a head-on, headto-tail, tail-to-head, broadside or any oblique collision of a predetermined magnitude will cause the breaker 80 to gain or lose sufficient momentum laterally that it places an unacceptable stress on the frangible tube intermediate the ends of the frangible tube, thus causing the frangible tube to break. When the frangible tube breaks, the upper spring forces the movable contact down, thus opening the switch and disconnecting the two stationary contacts 24 from electrical contact with one another. In the instance where the impact switch is connected in the circuit of the automotive electrical storage battery, the opening of the switch will disconnect the battery from the circuit, lowering the danger potential thereof.

In order to ensure desired operation of the device, electrical insulation may be provided where required, leg at 90, and mechanical shock insulation may be provided where required, e.g., at 92.

The term automobile is used generically to include any vehicle which could benefit from having the switch of the invention incorporated in the battery circuit thereof.

In the preferred embodiment, the housing is made of Bakelite or other insulating plastic material; the frangible tube is made of low strength glass, the contacts may be made of steel, aluminum, copper-clad steel, copperclad aluminum or the like; the breaker may be made of cast iron, mild steel, weighted thermoplastic material or the like.

A bracket 94 is shown provided on the outside of the housing for mounting the switch 10, e.g., on the engine compartment wall 96 of a vehicle, near the battery to be served by the switch.

It should be apparent that the cylindrical glass tube is equally subject to being broken by a force transmitted in any horizontal direction by the angularly symmetrical breaker 80.

The predetermination of the magnitude of collision needed to send the breaker destructively against the frangible tube is a matter for government and/or industry safety authorities to decide. As an example, a 10 mile per hour collision force could be selected as the threshold. Obviously, the switch lower cover could be removed and the broken frangible tube removed and replaced by a sound one and the switch reassembled after a collision-caused actuation of the switch.

It should now be apparent that the impact-opening electrical switch as described hereinabove possesses each of the attributes set forth in the specification under the heading Summary of the Invention hereinbefore. Because the impact-opening electrical switch of the invention can be modified to some extent without departing from the principles of the invention as they have been outlined and explained in this specification, the present invention should be understood as encompassing all such modifications as are within the spirit and scope of the following claims.

What is claimed is:

1. An impact-actuated electrical switch comprising:

a housing having a sidewall and two opposite end walls;

two stationary electrical contacts mounted in said sidewall so as to protrude into and out of the housing, the two stationary electrical contacts having inner ends disposed in a spaced relation within the housing;

a movable electrical contact mounted within the housing for movement between one position wherein the movable electrical contact bridges and electrically connectsthe inner ends of the two stationary electrical contacts, and another position wherein the movable electrical contact is spaced from at least one of the two stationary electrical contacts;

an upright frangible element mounted in said housing and engaging and holding said movable electrical contact in said one position thereof; and

an annular breaker element received within the housing loosely circumferentially surrounding the upright frangible element, whereby a generally horizontally directed change of momentum from any direction will shift the annular breaker element into crushing engagement with the upright frangible element, permitting the movable electrical contact to move to the other position thereof, thus disconnecting the two stationary contacts from one another, the inner ends of the two stationary electrical contacts being angled downwardly, the outer ends of the movable electrical contact being angled correspondingly upwardly, the other position of the movable electrical contact being below the one position thereof; and said upright frangible element, when intact, propping up the movable electrical contact via engagement with the underside of the movable electrical contact; and compression coil spring means disposed between the upper end wall of said housing and the top side of the movable electrical contact, said compression coil spring being at least partly compressed when the upright frangible element is in an intact condition so that when the upright frangible element is crushed, the compression coil spring, in being restored to a less compressed state, will force the movable electrical contact from the one position thereof toward the other position thereof.

2. The impact-actuated electrical switch of claim 1 further including second compression coil spring means of lower force constant than the first-mentioned compression coil spring means; the second compression coil spring means being mounted between the top side of the lower end wall of the housing and the underside of the movable electrical contact member and assisting the upright frangible element, while the latter is intact, in supporting the movable electrical contact member in said one position thereof; the second compression coil spring being insufficiently strong to maintain the movable electrical contact member in said one position thereof, against the action of the firstmentioned compression coil spring, absent assistance from the upright frangible element.

3. The impact-actuated electrical switch of claim 1 wherein the upright frangible element is an elongated glass element of round transverse cross-sectional shape.

4. The impact-actuated electrical switch of claim 3 10 jecting breaker bead means in the bore thereof positioned for crushing engagement with the elongated glass element upon lateral shifting of the annular breaker element.

7. The impact-actuated electrical switch of claim 1 wherein each stationary electrical contact includes means defining an outwardly opening socket in the outer end thereof, exteriorly of the housing; and fastener means adjustably constricting each socket for securing an electrical cable end therein. 

1. An impact-actuated electrical switch comprising: a housing having a sidewall and two opposite end walls; two stationary electrical contacts mounted in said sidewall so as to protrude into and out of the housing, the two stationary electrical contacts having inner ends disposed in a spaced relation within the housing; a movable electrical contact mounted within the housing for movement between one position wherein the movable electrical contact bridges and electrically connects the inner ends of the two stationary electrical contacts, and another position wherein the movable electrical contact is spaced from at least one of the two stationary electrical contacts; an upright frangible element mounted in said housing and engaging and holding said movable electrical contact in said one position thereof; and an annular breaker element received within the housing loosely circumferentially surrounding the upright frangible element, whereby a generally horizontally directed change of momentum from any direction will shift the annular breaker element into crushing engagement with the upright frangible element, permitting the movable electrical contact to move to the other position thereof, thus disconnecting the two stationary contacts from one another, the inner ends of the two stationary electrical contacts being angled downwardly, the outer ends of the movable electrical contact being angled correspondingly upwardly, the other position of the movable electrical contact being below the one position thereof; and said upright frangible element, when intact, propping up the movable electrical contact via engagement with the underside of the movable electrical contact; and compression coil spring means disposed between the upper end wall of said housing and the top side of the movable electrical contact, said compression coil spring being at least partly compressed when the upright frangible element is in an intact condition so that when the upright frangible element is crushed, the compression coil spring, in being restored to a less compressed state, will force the movable electrical contact from the one position thereof toward the other position thereof.
 2. The impact-actuated electrical switch of claim 1 further including second compression coil spring means of lower force constant than the first-mentioned compression coil spring means; the second compression coil spring means being mounted between the top side of the lower end wall of the housing and the underside of the movable electrical contact member and assisting the upright frangible element, while the latter is intact, in supporting the movable electrical contact member in said one position thereof; the second compression coil spring being insufficiently strong to maintain the movable electrical contact member in said one position thereof, against the action of the first-mentioned compression coil spring, absent assistance from the upright frangible element.
 3. The impact-actuated electrical switch of claim 1 wherein the upright frangible element is an elongated glass element of round transverse cross-sectional shape.
 4. The impact-actuated electrical switch of claim 3 wherein the glass tube is received between detent means on the underside of the movable electrical contact and on the top side of the lower end wall of the housing.
 5. The impact-actuated electrical switch of claim 3 wherein the elongated glass element is tubular.
 6. The impact-actuated electrical switch of claim 3 wherein the annular breaker element includes at least one circumferentially extending, radially inwardly projecting breaker bead means in the bore thereof positioned for crushing engagement with the elongated glass element upon lateral shifting of the annular breaker element.
 7. The impact-actuated electrical switch of claim 1 wheRein each stationary electrical contact includes means defining an outwardly opening socket in the outer end thereof, exteriorly of the housing; and fastener means adjustably constricting each socket for securing an electrical cable end therein. 